Predictor Variable
自变量
Experimental Variable
因变量，实验变量
Control Variable
1. list all potential var
2. if have no data, remove var
3. combine similar var
4. test the correlation between predictor and outcome
Lurking Var? Logic
we thought A -> B, but in fact C->A, C->B. So A-/->B, but C->B.
How Long?
Full Cycle
Design Unit
1. Randomized
random treatment unit, control
2. Matched Pair
a treatment unit <-> a similar control unit
